Stabilized oxidizable hydrocarbon oil



' mama Feb. 27, 1951 STABILIZED OXIDIggLE HYDROCABBON William '1'. Stewart and James 0. Clayton, Berkeley, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application November 8, 1948, Serial No. 59,027

Claims. I

This invention relates to the art of improving organic substances by incorporating therein a small amount of an added agent which stabilizes the organi substance against oxidation, or reduces corrosiveness of said substance to particular kinds of metallic surface, or acts to disperse sludge in said substance and prevent deposition of sludge on hot surfaces, or acts to prevent formation of sludge, or which functions to accomplish several of these objects.

More particularly, this invention relates to improving hydrocarbon oils of lubricating viscosity, such as mineral oil, motor, gear and turbine lubricants, transformer oils, mineral oil-soap greases, and the like, by adding thereto a small amount of an agent which stabilizes the oil against oxidation, or inhibits corrosion of cadmium-silver and lead-copper types of alloy bearings, or functions to prevent deposition of sludge and carbon on pistons and in piston ring slots of internal combustion engines, or functions to accomplish several of these results.

In the search for improved mineral lubricating oils, several desiderata are present, varying in importance from one type of service to another. Enhanced film strength (i. e., the ability of a lubricant to maintain a film of lubricant between relatively moving surfaces at extremely high pressures), resistance to discoloration on exposure to the normal atmosphere, as in storage of a lubricant, resistance to oxidation on exposure to air or other oxidizing gases at high temperatures as in transformers and in the lubrication of cylinders of internal combustion engines and the working parts of steam and gas turbines, and resistance to fouling of cylinders of internal combustion engines, are among the desired properties of lubricants and other mineral oil compositions.

It is an object of the present invention to provide a new class of materials for addition to oxidizable organic substances to satisfy one or more of the desiderata mentioned above.

It is a further object of the invention to provide compositions of matter comprising in major part an oxidizable organic liquid and containing a small amount of added organic substance which as such greatly enhances resistance of the composition to oxidation.

It is a further object of the invention to provide hydrocarbon lubricating oils and the like having high resistance to oxidation.

It is a further object of the invention to provide hydrocarbon lubricating oils of enhanced resistance to oxidation and to formation and deposition of sludge, and of reduced tendency to corrode cadmium-silver, copper-lead and other similar bearing alloys.

It is a particular object of the invention to provide mineral lubricating oils which are of enhanced utility as lubricants at high temperatures and in the presence of oxidizing gases, by reason of enhanced resistance to oxidation and reduced tendency to form or to deposit sludge on hot metal surfaces. or v It is a further particular object of the invention to provid mineral oil lubricants for use in lubricating the pistons of internal combustion engines, especially of those engines, such as Diesel and aircraft engines, which operate under high compression and at high temperatures.

It is also an object of the present invention to provide a class of addition agents for mineral oil lubricants which combine in marked degree a capacity to inhibit oxidation of the oil, corrosion of alloy bearing, and fouling of pistons of internal combustion engines.

It is also an object of the present invention to provide new, oil-soluble mineral oil improvement agents and a ready means of preparing the same.

It is also an object of the present invention to provid new combinations of mineral lubricating oil improvement agents, by means of which still more marked improvements and a greater variety of improvements are obtained.

Still further objects will be apparent from the ensuing description and the appended claims.

We have discovered that a certain class of selenium compounds, embracing many com pounds in themselves new, when present in small amount in a substantially non-reactive oxidizable organic substance, impart marked improvements to the organic substance.

wherein (reading from left to right), R1, R2 and R3 are hydrogen or organic radicals (any two of which may be joined to form a single, bivalent radical), C is an aliphatic carbon atom (i. e., a carbon atom other than a carbon atom forming part of a benzenoid ring), and X is selenium or tellurium.

The simplest member of this clas is methyl selenomercaptan, CHzSeH. Although it is operative as an improvement agent when added in small amount to mineral lubricating oil and the like, it is volatile and not as well suited for use under conditions of high temperature as are higher molecular weight, less volatile compounds. Other similar low molecular weight selenomercaptans and telluromercaptans are likewise less desirable than the higher molecular weight (hence less volatile, less odorous and more oilsoluble) compounds. The preferred compounds of the invention are those containing 5 to 30 carbon atoms, most advantageously to 30 carbon atoms in the molecule. As stated, the selenium compounds are preferred to the tellurium compounds.

Examples of selenium and tellurium compounds of the invention are n-butyl, n-amyl, 2-ethylhexyl, decyl, lauryl, cetyl, octadecyl, and paraffin selenomercaptans and 2-ethylhexyl, lauryl and octadecyl telluromercaptans. Other radicals (e. g., other alkyl radicals such as ethyl, nand isopropyl, isobutyl, isoamyl, hexyl, undecyl and tetradecyl, aralkyl radicals such as benzyl and cetylbenzyl and cycloaliphatic radicals such as cyclohexyl and methyl cyclohexyl) may be used in place of the above mentioned radicals, and the organic radical attached to selenium may contain an unsaturated group or may be substituted by a non-hydrocarbon substituent such as chlorine, hydroxyl, alkoxyl, amino, etc.

By parafiin as used herein to designate an organic radical is meant a radical derived from paraffin wax; e. g., parafiin selenomercaptan is a selenomercaptan (actually, a mixing of selenomercaptans) such as can be prepared by using chlorinated parafiin wav as the organic chloride, R.Cl, in Equation 2 below.

By aliphatic as used herein without qualification to designate an organic radical attached to selenium or tellurium, is meant an organic radical whose attachment to selenium or tellurium is through a non-benzenoid carbon atom; e. g., octadecyl, benzyl and cyclohexyl selenomercaptans are all aliphatic selenomercaptans as aliphatic is herein defined.

The selenomercaptans can be prepared by the following series of reactions:

Sodium diselenide is prepared by Reaction 1 and is reacted with an aliphatic chloride (RC1) in accordance with Reaction (2) to yield an aliphatic diselenide (R-SeSeR). The aliphatic diselenide is reduced in accordance with Reaction 3 to yield an aliphatic selenomercaptan.

In Reactions 1, 2 and 3, potassium or other metal may be substituted for sodium, tellurium may be used instead of selenium and bromine or other replaceable element or radical may be substituted for chlorine. The group R is an aliphatic group. If a mixed diselenide is available, e. g., ethyl cetyl diselenide (C2H5- SeSe Ciel-I33) it may be substituted for the symmetrical diselenide of Reaction 3, yielding a mixture of selenomercaptans (e. g., ethyl and cetyl selenomercaptans).

The selenium and tellurium compounds of the invention may be used in amounts as low as 0.01 or less or as high as 5% or more, but preferably they are used in amounts of 0.1 to 2%, percentages being by weight based on finished composition. Concentrates or stock solutions containing 5 to 50% or more of the selenium compound of the invention dispersed in an organic liquid (e. g., mineral lubricating oil) may be prepared for later blending with the substance to be stabilized to produce a finished product.

The selenomercaptans are incorporated in various oxidizable organic substances, particularly organic liquids, which substances are substantial- 1y unreactive with the added selenomercaptans so.

that the latter inhibiting agent is not dissipated by reaction with the substance to be inhibited but rather remains as selenomercaptan to inhibit oxidation. Thus, of the oxidizable hydrocarbon oils, those which are substantially completely free from olefins (which are said to react with selenomercaptans) are employed; thus, the substantially completely saturated hydrocarbon oils are preferably treated in accordance with the present invention, and unsaturated hydrocarbons, such as cracked gasoline, are excluded. Thus, the addition of selenomercaptans to lubricating oils causes no spontaneous reaction or color change; likewise the selenomercaptans remain unchanged in hydrocarbon solvents, such as petroleum ether, which is employed for extraction in the preparation of selenomercaptans. In other words, the present additives are employed in oxidizable organic substances which are stable to selenomercaptans, i. e., which are substantially free from groups normally reactive with selenomercaptans and telluromercaptans.

Illustrative of organic substances to which the selenium compounds of the invention may be i added as stabilizers are petroleum products such as saturated gasoline, kerosene, lubricating oils and mineral oil-soap greases; saturated fats, fatty oils, rubber, aldehydes, ethers, terpenes, mercaptans, phenols and synthetic plastic or resinous materials such as urea-formaldehyde, polyvinyl and phenolformaldehyde resins. These and other organic materials undergo oxidation and deterioration (e. g., discoloration, sludge formation, thickening, etc.) under conditions ranging from mere exposure to air at normal atmospheric temperature to intimate admixture with air or other oxidizing gases at temperatures of 300-400 F. The inherent stability of the organic material toward oxidation will, of course, vary with the material. The selenium compounds of the invention will stabilize such materials under mild to extreme conditions of oxidation.

The following specific examples will serve further to illustrate the practice and advantages of the invention.

Example 1. Preparation of high molecular weight selenomercaptans.-Methods described in the literature for preparing selenomercaptans are the reaction of sodium or magnesium hydroselenides with an alkyl halide or alkyl metal sulfate, and the reaction of aluminum selenide with alcohols at elevated temperatures. See, for example, J. Newton Friend's "Textbook of Inorganic Chemistry," vol. XI, part IV, page 1 (1937). These methods are disadvantageous because large amounts of dialkyl selenides and dialkyl diseienides are formed by side reactions. This necessitates the recovery of the selenomercaptan by distillation. When applied to the preparation of high molecular weight selenomercaptans. i. e., those containing about carbon atoms or more,

" these methods of the prior art are especially disadvantageous because of the tendency of the high molecular weight selenomercaptans to decompose on distillation.

We have discovered a much superior method of preparing high molecular weight selenomercaptans which will now be described with reference to octadecyl selenomercaptan.

Dioctadecyl diselenide was prepared as follows: A mixture of 2 gram moles of sodium diselenide, 2 gram moles of octadecyl chloride and one liter of 95% ethyl alcohol were refluxed and stirred for nine hoursl The reaction mixture was diluted with one liter of water and extracted with petroleum ether. The petroleum ether extract was dried over anhydrous sodium sulfate, filtered and concentrated on a steam bath. Two volumes of a 50% mixture of petroleum ether and acetone were added and the solution was cooled to promote crystallization of the dioctadecyl diselenide. A yield of 602 grams of dioctadecyl diselenide was obtained in the form of lemon yellow crystals melting at 52 C. to 55 0. Analysis. Found: percent Se=22.3. Theoretical: percent Se=23.8.

A mix are of 30.4 grams of dioctadecyl diselenide and 34 mls. of 50% (by weight) sulfuric acid was heated to reflux temperature and 8.7 grams of zinc dust wereadded gradually with vigorous stirring. After addition of the zinc dust had been completed, 5 mls. of concentrated sulfuric acid were added and refluxing and stirring were continued until the zinc had completely reacted. On cooling the mixture to room temperature, octadecyl selenomercaptan separated as a white crystalline layer. This product was a white, waxy, crystalline solid melting at 36 to 40 C.

The octadecyl selenomercaptan so prepared can be reacted with alcoholic solutions of metal hydroxides or metal acetates to yield the desired metal selenomercaptide, or it can be dissolved in aqueous or aqueous-alcoholic sodium or potassium hydroxide and treated as described above.

Example. 2. Preparation of zinc octadecyl selenomercaptide.-The product of Example 1 (product of reducing 30.4 grams of dioctadecyl diselenide) was extracted with petroleum ether and the extract was washed with water, dried over sodium sulfate, filtered and mixed with 200 ml. of 95% ethyl alcohol. Petroleum ether was removed by distillation and 250 m1. of 95% ethyl alcohol were added to the residue. This mixture was heated to 150 F. and a solution of 18.3 grams of zinc acetate dissolved in 150 ml. of hot water was added slowly with stirring. A white precipitate formed, which was collected on a filter, washed with water, then with alcohol and then with petroleum ether and dried in vacuo over calcium chloride. A yield of 22 grams of zinc octadecyl selenomercaptide was obtained.

being 65% on the crude dioctadecyl diselenide. This product was found to contain 20.7% Se (theoretical, 21.6%) and 8.91% Zn (theoretical, 8.95%). In subsequent preparations, the yield was raised to 84%. The product was a white solid soluble in chloroform and benzene, slightly soluble in alcohol.

Example 3. Preparation of cadmium octadecyl selenomercaptida-A solution of 70.4 grams of cadmium acetate dihydrate in 300 ml. of hot 50% ethyl alcohol was added slowly with stirring to a hot mixture of 160 grams of octadecyl selenomercaptan and 300 m1. of 100% ethyl alcohol. The precipitated cadmium octadecyl selenomercaptide was collected on a filter, washed with water, alcohol and acetone and dried in vacuo over calcium chloride. The product weighed 188 grams, representing a yield of 60% based on cadmium content. Analysis. Found: Cd=8.7%, 8.8%; se=16.6%, 16.8%. Theoretical: Cd=14.5%, Se=20.3%. After extraction with boiling petroleum ether, the product weighed 145 grams and assayed 11.5% Cd and 19.8% Se. The product was a white solid. soluble in chloroform and benzene and slightly soluble in alcohol. The product was about pure.

Example 4. Preparation of lead octadecyl selenomercaptide-A hot solution of 91.2 grams of basic lead acetate (Pbz(OH)Ac3) in 350 m1.

of 50% ethyl alcohol containing 9 grams of glacial acetic acid was added slowly with stirring to a heated mixture of 200 grams of octadecyl selenomercaptan and 350 ml. of 100% ethyl alcohol. The precipitate was filtered off, washed with hot water, alcohol and petroleum ether. After drying in vacuo over calcium chloride the prodduct weighed 205 grams, representing a yield of 78% based on lead content. Analysis. Found: Pb=23.5%.; Se=17.7%. Theoretical: Pb=23.8%; Se=18.1%. The product was a salmon colored solid, soluble in chloroform and benzene, and slightly soluble in alcohol.

Example 5. Preparation of barium octadecyl selenomercaptide.-A slurry of 43 grams of barium oxide in 200 ml. of ethyl alcohol and 5 ml. of water was added with stirring to a refluxing mixture of 180 grams of octadecyl selenomercaptan and 200 ml. of 95% ethyl alcohol. Refiuxing was continued for twenty-five minutes and the reaction mixture was allowed to cool. The precipitate was collected on a filter, washed with alcohol and petroleum ether and dried in vacuo over calcium chloride. The pfoduct weighed 184 grams representing a yield of 77% based on barium content. Analysis. Found: Ba=15.8%; Se=17.6%. Theoretical: Ba=l7.1%; Se=19.7%. The product was slightly soluble in chloroform and benzene.

Example 6. Preparation of nickel octadecyl selenomercaptide.A hot solution of 69.2 grams of nickel bromide in 250 nil. of 50% ethyl alcohol was added with stirring to a heated mixture of 214 grams of octadecyl selenomercaptan and 350 m1. of ethyl alcohol. Stirring was continued while a solution of 25.8 grams of sodium hydroxide in ml. of hot water was added slowly. The precipitate was collected on a filter, washed with acetone and dried in vacuo over calcium chloride. The product weighed 242 grams. Analysis. Found: Ni=6.8%, 6.8%; Se=16.1%, 16.2%. Theoretical: Ni=8.l%; Se=22.0%. Fractionation of the product showed it to be a mixture of nickel octadecyl selenomercaptide (38%), octadecyl se- 76 lenomercaptan and dioctadecyl diselenide (37%) and inorganic nickel compounds. The crude product was a granular, black solid, soluble in chloroform and benzene.

In each of the preparations described in Examples 1 to 6, above, the reaction mixture and product were blanketed by an atmosphere of nitrogen to prevent oxidation, until such time as the final product was prepared.

Example 7. Oxidator tests.-Selenium compounds of the invention, also, for comparison, certain selenium compounds not of the invention, were dissolved in small amount in medicinal grade of white oil and submitted to an oxidation test in an apparatus of the type described by Dornte in Industrial and Engineering Chemistry, vol. 28, page 26 (1936), oxygen being bubbled through the oil at atmospheric pressure. The temperature of the oil was 340 F. Results are given in Table I below, the Induction Period being the time in hours required for 100 gms. of oil to absorb 1200 cc.*of oxygen measured at S. T. P.

Table I Induction Additive Se Period Percent Hours Nil 0. 0.08% Dioctadecyl diselenide 0. 019 2. 5 0.1% Dilauryl selenide 0. 019 2. 5 0.159 0 Dilauryl selcnide 0. 03 3. 9

0.08 0 Octadecyl selcnr mercaptan 0.019 4. 4 I 0.1597 Zn octadecyl scl tnomcrcapti ie 0. 0344 4. 8 0.149 0 Cd octadecyl selcnomercaptiic 0. O3 2. 1 0.166% Pb octadcc'yl selenomercaptide 0. 03 0. 8 0.153% Ba octadecyl selcnomercaptide 0. 03 3. 9 0.1387 Ni octadecyl selen0mercapt1le. 0.03 3. 6 0.086 0 Zn 2-ethyl hexyl selenomercaptrda- 0. 051 1.8

It will be seen from the above table that all of the additives of the invention greatly improved the base oil. The free selenomercaptan was superior to dioctadecyl and dilauryl selenides. The metal selenomercaptides were not aseifective oxidation inhibitors as the selenomercaptan, but several were as effective as dilauryl selenidc and all of them greatly improved the base oil.

As oxidation inhibitors the free selenomercaptans are preferred to their salts, but their salts, especially the polyvalent metal salts, have in greater degree the property of functioning asfdetergents" in motor lubricants; i. e., they promote cleanliness of pistons, piston rings and piston ring slots and retard piston ring sticking in internal combustion engines. This is shown in Example 8 and Tables II and III below.

Example 8. Strip corrosion and engine tests.- Wrious oils, both uncompounded and compounded with small amounts of additives as indicated in Tables II and Ill below, were submitted to strip corrosion and engine tests as follows: In the corrosion tests, thin strips of copper-lead alloy of the type used in bearings of internal combustion engines are immersed in oil. The oil is maintained at 300 F. and air is blown through the oil during the test. Corrosion loss is noted after each test. Further details of this test appear in Farrington et 9.1. U. 8. Patent No. 2,349,817 at page 3, right-hand column, lines 17 to 37. The Lauson engine tests Were carried out in the manner described in the same patent, page 3, left-hand column, lines 14 to 26, except that observations were made only at 30-hour intervals, crankcase (sump) temper- The Wisconsin tests were carried. out in a single cylinder air cooled Wisconsin engine, 2% inch bore and 2% inch stroke, loaded by means of an electric induction motor. The engine was operated under extremely severe conditions, designed to develop fully the tendency of the crankcase lubricant to deteriorate with gum formation and piston ring sticking. Operation was at 1300 R. P. M.; upper cylinder temperaturewas maintained at 600 F.; crankcase oil temperature was maintained at 220 F. At periods of 30 hours the operations were interrupted and the condition of the piston and piston rings determined.

The results of these tests are set forth in Tables II and III below. In the tables, the concentration of each additive, if it is 'a salt, is" given as millimols of metal per kilogram of oil; e. g., "14 mM/kg.Zn octadecyl selenomercaptide," which means 14 millimols of zinc, in the form of zinc selenomercaptide, per 1000 grams of oil. This particular salt was a relatively pure compound (C1aHa7Se)zZn, and has a molecular weight of 729. Therefore, 14 mM/kg. of this salt amounts to 1% by weight salt based on the oil. In most other cases the mM/kg. of metal can be similarly converted to per cent by weight of salt but in a few cases, e. g., calcium sulfonate, the molecular weight of the salt being unknown, it is impossible to convert mM/kg. of metal to per cent of salt.

Further with regard to Table II: The calcium sulfonate was a synthetic product made by chlorinating white oil, then condensing it with benzene, sulfonating the condensation product and converting the sulfonic acid to its calcium salt. The calcium phenate was prepared by condensing a butene polymer (average molecular weight about 194) with phenol and forming the calcium salt of the condensation product, as described in Examples 1 and 3 of Gardiner et 9.1. U. S. Patent No. 2,228,661. The sulfurized calcium phenate was prepared by heating the same calcium phenate with sulfur, as described in Etzler et a1. U. S. Patent No. 2,360,302. The zinc dicetylphenyl dithiophosphate was the product of reacting two moles of cetyl phenol, one mol of Pass and one mole of ZnO. The sulfurized diparaffin sulfide was the product of reacting chlorinated paraffin (22% chlorine) wih sodium polysulfide to yield a product containing 14% sulfur and 3% chlorine and heating this sulfurand ch orine-containing product with free sulfur in the proportions of and 4.2,respectively,at300 F. until all the sulfur dissolved. The said sulfurand chlorine-containing product can be prepared in the manner described in Example 1 of Farrington et al. U. S. Patent No. 2,346,156. All the salts of Table II were normal sa ts. Base Oil A was a solvent refined SAE 30 parafiinic oil of California origin. Base Oil B was a solvent refined SAE 30 Mid-Continent oil. Oil C was a solvent refined SAE 50 paraillnic oil of California origin.

- In these tables, PD No. designates piston discoloration number. By piston discoloration number is meant this: After 30 hours and again after 60 hours, the engine is dis-assembled and the piston is inspected. To a piston skirt which is completely black is assigned a PD No. of 800; to one which is completely clean is assigned a PD No. of zero; to those intermediate completely black and completely clean are assigned PD Nos. in proportion to the carbonaceous deposits, Actually, further refinements were employed in arriving at PD Nos. hereinbelow disclosed, but since the same method was used in every case it is urmecessary to describe these refinements.

Table lip-Strip corrosion and Lesson engine I tats snip Cwrolion, Wt. ngine Tests.

Lou, mp. D No. Additives 24 hrs. 48 hrs. 72 hrs. 80 hrs. N hrl.

A Nil... 108.7 400 A 14 mM/kg. Ca suiiona 52. 2 150 A 14 mM/kg. Zn octsdecyl selenomerceptido 25, 2 70 310 A 14 mM/kg. Cd octadecsi selenomercaptide.-- +6.5 130 155 A 14 mM/kg. Sulfurized a am as A 7 mM/kg. Zn octadecyl selenomermptidwiuliurired O phm'mha +5.1 +8.5 +l1.3 110 215 A 7 mM/kg. Pb octadecyl selenomercaptidei-Bnliurlud Ca phnn Am +6. 1 +4. +3. 1 1 A 14 mM/kg. 0a phena 225 850 A 7 mM/kg. Zn octadecyl selenomercaptidei-Cs phonon--. 8. 8 19. 32.0 A 7 mM/kg. 0d octadecyl selenomcrcaptide+0s phenom.--" 10. 4 l8. 0 20.0 A 7 mM/ka. Ba oetadecyl selenomercaptide+0a pbenate.. 91.0 02. 98. 5 8) A 7 mM/kg. Ca suli'onate+7 mM/kg. Zn octadec'yl solenomermpfldn 6 +6. 8 7 25 88 Table 1II.--Strip corrosion and engine tests Bizip Corrosion, Wt. Engine Tests. BM has. mas- D No. a on Adam 2481's. 481111. 121m. mam. 608m.

B Reference Compounding 1. 1 1. 4 2. 9 an m B 4.5 mM/kg. suliurized Ca phenste+4.5 mM/kg. Ca +5.8 +8.1 +6.7 5 10 Do.

suli'onate+6 mM/kg. Zn octadeoyi selenomercaptide. B 9 mK/kg. Ca phenate+6 mM/kg. Zn octadecyl seien- 50 G) De.

omercaptide. 0 Nil. 1. 3 4. 4 21. 0 466 Wisconsin. 0 0.8% Octadecyl seienomercaptan+l6 mM/kg. Ba I 1.3 7.0 16.0 75 Do.

cetoxy phenate. C 16 mM/kg. Zn octadecyi selenomercaptido 0.1 +1. 0 +12. 5 215 32) Do. 0 8 mM/kg. Zn octadecyl selenomercaptide-l-B mid/kg. +0.5 +7.0 +0.0 140 145 Do.

Ba m-cetoxy phenate. O 8 mM/ka ga phenate+8 mM/kg. Zn octadecyi sslenir 8. 1 26. 0 41.4 145 Do.

mercap e. O 14 mM/kgflga phenate+l4 mM/kg. Zn octadecyl soleno- 17. 8 18. 1 3i. 4 105 135 Do.

meroan e. C 24 mM/kg. Ca lifluanate-l-li mM/kg. Zn octadecyi se- 5.8 4.2 7.2 155 D0.

ienomercapti e. O 7 mM/kg. Ba m'cetoxy phenate+7 mM/kg. Pb octa- 0.0 9.1 9.4 100 Do.

decyl seienomercsptide.

In Table IV below are given still further data, showing the performance of a low molecular weight selenomercaptide (zinc z-ethyl hexyl selenomercaptide, made from Z-ethyl hexyl chloride) and of a high molecular weight selenomercaptide (zinc paraflin selenomercaptide, made from a chlorinated, low melting paramn wax). Base oils A and C are the same as base oils A and C above.

exacting test requirements of Army Ordnance 2-1043 Specification. The superiority of the compounding of the present invention is evident from Table III.

One or more selenium compounds of the invention may be used as the only added material present in an oxidizabie organic substance or they may be used in conjunction with other additives. For example, the selenium compounds of the Table IV Strip Common-Wt. Enilgfi gesta- Base a on Additives 57.13

Mhrs. 481m. 721m. 301m. 601m.

A 4.5 mK/kg. Ga suifonate+45 mM/kg. sulfnrized Ca +11.5 +13.0 +l2.5 0 0 lemon.

phenate+6 mM/kg. Zn z-etbyl hexyl seienomerca tide. O 20 rlnM/kg. Catfihenate+l0 mM/kg. Zn Z-ethyl exyl 7.8 8.5 2.3 100 225 Wisconsin.

seenomercap e. O Ca phenate+8 mM/kg. Znpcraflinselenomer- +0.4 +214 +21.4 40 50 Do.

cap e.

The data in Tables II, III and IV illustrate, among other things, the following: Most of the selenium compounds of the invention functioned to inhibit corrosion of copper-lead bearings. All of them functioned to promote piston cleanliness, as shown by the PD numbers. Especially good results were obtained with combinations of addition agents, such as the phenate-selenomercaptide, sulfurized phenate-selenomercaptide and sulfonate-selenomercaptide combinations.

The "Reference compounding" in base 011 B invention may be used advantageously in mineral lubricating oils in conjunction with metal salts of organic acids and/or metal salts of creamsubstituted inorganic acids. These salts are used to improve various properties of lubricating oils. such as detergency, stability against oxidation, film strength, etc. Examples of such metal salts are calcium, barium, zinc and aluminum salts of cetylphenol; calcium, barium, zinc and aluminum salts of diamyl dlphenol monosulflde; calcium, barium, zinc and aluminum salts of-monoand dicetyl esters of phosphoric acid; calcium, barium,

was a multiple compounding which has 75 zinc and aluminum salts of monoand dlcetylphenyl esters of dithiophosphoric acids; calcium, barium, zinc and aluminum salts of naphthenic acids; calcium, barium, zinc and aluminum salts of oil-soluble petroleum (mahogany) sulfonic Rutherford U. S. Patent No. 2,363,012. Other metals (e. g., sodium, lithium, magnesium and cobalt) and other acid radicals (e. g., aryl carboxylic acid, fatty acid, aliphatic polycarboxylic and thiophenol radicals) may be used instead of the aforementioned calcium, barium, zinc and aluminum metals and the aforementioned phenate,"phenate sulfide, phosphate, thiophosphate, naphthenate, sulfonate and dithiocarbamate radicals, respectively. Thus, from 0.1 to 2% of selenium compound and from 0.1 to 2% of metal salt may be added to mineral'lubricating oil, or greater amounts may be used to form a concentrate or stock solution.

The selenium and tellurium compounds 01' the present invention are also useful to improve the film strength of lubricants, as shown by the following data:

.Table V Failure (Weeks Testing Ma chine, 600 R P. M.) at- Pounds Solvent refined SAE 30 oil 100 Solvent refined SAE 30 oiI-|-0.5l% octadecyl selenomercaptan 180 Solvent refined SAE 30 oil+0.56% Zn octadecyl selenomcrcaptide 340 cient to inhibit oxidation of said oil, of a compound of the structure wherein X is selected from the group consisting of selenium and tellurlum, R. is an aliphatic group of 5 to 30 carbon atoms and H is hydrogen.

2. A lubricant comprising a major proportion of an oxidizable hydrocarbon oil of lubricating viscosity which is substantially free from groups, including unsaturated groups, normally reactive with organic selenoand telluric-mercaptans, and a small amount, suflicient to inhibit oxidation of said oil, of a compound of the structure wherein X is selected from the group consisting of selenium and tellurium, R is an aliphatic group containing 5 to 30 carbon atoms, and H is hydrogen.

3. A lubricant comprising a major proportion of an oxidizable hydrocarbon oil of lubricating viscosity which is substantially free from groups, including unsaturated groups, normally reactive with aliphatic selenomercaptans, and a small amount, suflicient to inihibit oxidation of said oil, of an aliphatic selenomercaptan of 5 to 30 carbon atoms.

4. A mineral oil composition comprising a major proportion of mineral oil of lubricating viscosity, which oil is substantially free of groups, including unsaturated groups, normally reactive with aliphatic selenomercaptans and about 0.1 to 2% by weight based on finished composition of an aliphatic selenomercaptan containing 5 to 20 carbon atoms in the molecule.

5. The composition of claim 3, wherein said selenomercaptan is octadecyl selenomercaptan.

WILLIAM T. STEWART. JAMES O. CLAYTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,835,184 Rosenstein et al. Dec. 8, 1931 1,966,050 Sloane July 10, 1934 2,295,053 Rosen Sept. 8, 1942 

1. AN INHIBITED OXIDIZABLE HYDROCARBON OIL WHICH IS SUBSTANTIALLY FREE FROM GROUPS, INCLUDING UNSATUREATED GROUPS, NORMALLY REACTIVE WITH SELENOMERCAPTANS AND TELLUROMERCAPTANS, SAID OXIDIZABLE OIL CONTAINING A SMALL AMOUNT, SUFFICIENT TO INHIBIT OXIDATION OF SAID OIL, OF A COMPOUND OF THE STRUCTURE 